Recently, for example, a liquid crystal display device has been used widely in a liquid crystal television, a monitor, a mobile telephone, and the like as a flat panel display having advantages such as smaller thinness and lighter weight compared with those of conventional Braun tubes. Such a liquid crystal display device includes an illumination device emitting light and a liquid crystal panel displaying a desired image by playing a role as a shutter with respect to light from a light source provided in the illumination device.
Furthermore, as the above-mentioned illumination device, an edge-light type device or a direct-type device has been provided, in which a linear light source composed of a cold cathode-ray tube or a hot cathode-ray tube is placed on the side of or below a liquid crystal panel. However, the cold cathode-ray tube and the like as described above contain mercury, so that it used to be difficult to recycle the cold cathode-ray tube to be discarded. Then, an illumination device using a light-emitting diode (LED) without using mercury as a light source has been proposed (see, for example, JP 2006-128125 A).
Further, in the conventional illumination device described in Patent document 1, it is shown that a plurality of driving elements for driving light-emitting diodes are placed on a mounting surface of a printed circuit board on which a plurality of light-emitting diodes are also mounted. According to this conventional illumination device, it has been concluded that the productivity of the illumination device can be improved by placing the plurality of light-emitting diodes and the plurality of driving elements on one printed circuit board.